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Biomedical subjects

A C Ferguson

Publications and source records attributed to A C Ferguson.

At least 37 records · Page 2Linked to original sources
PubMed1986

Predictive value of skin prick tests and radioallergosorbent tests for clinical allergy to dogs and cats.

The predictive value and post-test probability of disease were compared for skin prick tests and radioallergosorbent tests (RASTs) in 168 children suspected of clinical allergy to dogs and cats. The skin tests included negative and positive (histamine) controls. The results of RASTs with the same allergen extracts were expressed in relation to the results with allergen-specific pooled reference serum. All the tests were performed blind. The predictive values of positive test results were comparable and low (53% to 76%), whereas the predictive values of negative test results were comparable and high (88% to 95%). The post-test probability of clinical allergy to dog or cat allergen, based on the prevalence rates in the referral population (15.1% and 22.5% respectively), increased to between 46% and 67% for positive test results and decreased to between 4% and 8% for negative results, which suggests that the primary role of skin prick tests and RASTs is in eliminating the diagnosis of clinical allergy.

Adolescent↗
PubMed1985

Sensitization to house dust mites in different climatic areas.

With the use of local meteorologic data, the mean monthly indoor relative humidity (RH) was calculated for the area of residence of each of 774 children with respiratory symptoms who were referred to our allergy clinic. Seven hundred fourteen children lived in areas in which the mean indoor RH was 50% or more for 4 or more mo per year ("humid" areas), and 60 children lived where this RH was present for no more than 2 mo per year ("dry" areas). Of those children from the "humid" areas, the skin prick test was positive to Dermatophagoides farinae in 31% and D. pteronyssinus in 40%, whereas in those children from "dry" areas, tests were positive in 3% and 2%, respectively, (p less than 0.001). There was also a marked difference in the degree of sensitivity. In those children with a positive RAST (more than 12% of binding relative to allergen-specific pooled reference sera), the mean level of binding was 51% +/- 3.5% for D. farinae and 62% +/- 4.4% for D. pteronyssinus in children from "humid" areas but never exceeded 14% for either species in those children from "dry" areas (p less than 0.001). Sensitivity to D. farinae and D. pteronyssinus is frequent in "humid" areas and seldom, if it is ever, occurs in areas that are "dry," either as a result of a semiarid climate or a prolonged heating season. These findings have implications for the etiologic diagnosis and specific treatment of atopic patients living in different climatic regions.

Child↗
PubMed1984

Elevated IgG immune complexes in children with atopic eczema.

The levels of serum IgG complement-fixing immune complexes were studied in 20 children with atopic eczema and in 10 children with allergic rhinitis as control subjects with the use of a Raji cell assay. Immune-complex levels were strikingly elevated in those with eczema, 50 +/- 10 SE micrograms/ml, compared to control subjects 11 +/- 9 micrograms/ml (p less than 0.0047), the latter falling within the range for nonallergic subjects. Levels tended to be higher in those subjects with more severe eczema, but there was no statistically significant correlation, nor were levels correlated with serum IgE. Sucrose-density gradient analysis demonstrated the immune complexes to be present in two peaks, 8 to 10S and 21S or higher. High-molecular-weight IgG immune complexes that are complement-fixing may promote the characteristic pruritus of eczema by formation of anaphylactic complement fragments and the release of inflammatory substances from cutaneous mast cells, as well as contributing to the impaired cell-mediated immunity associated with the disease.

Antigen-Antibody Complex↗
PubMed1984

Food allergy.

Adverse clinical reactions to food associated with disturbed immunologic function (food allergy) affect 1-3% of the population and vary from life-threatening to a minor inconvenience. They must be differentiated from reactions caused by toxins, pharmacologic agents, enzyme deficiences and non-specific release of inflammatory mediator substances. Enteric absorption of food protein antigens which may occur despite an array of gastrointestinal protective mechanisms normally induces both a protective immune response and immunologic tolerance. Quantitative changes in absorption related to deficient protective mechanisms or excessive antigen load may contribute to the development of an allergic immune response and explain the greater incidence of food allergy in infants and children. Important factors include immunologic immaturity, enhanced macromolecular mucosal transport, intrauterine and neonatal malnutrition, breast feeding and infection. Double-blind food challenge tests remain as the most definitive diagnostic yardstick but carefully standardized skin tests may be helpful if interpreted in the context of the clinical history. Despite the association of food allergy with food antigen specific IgE hypersensitivity, immune complex formation and lymphocyte sensitization the pathophysiological changes which result in symptoms remain obscure. Recent advances have clarified many aspects of our knowledge of food allergy but inevitably have raised many more questions for future study.

Adolescent↗
PubMed1983

The frequency and severity of cat allergy vs. dog allergy in atopic children.

Questions were put to parents accompanying 1238 children, 1 to 17 yr old, who had symptoms of respiratory tract allergy. Skin prick tests were then performed. Symptoms after exposure to cats and positive skin test results from cat hair extract were significantly more frequent than symptoms after exposure to dogs or reactions to dog hair extract. The prevalence of symptoms and positive skin test reactions to cat allergens increased with age, significantly more so than the reaction or symptoms after exposure to dog allergens. The greater frequency of sensitivity to cats was not caused by exposure to cats in more homes, since dogs significantly outnumbered cats as the household pet in both atopic and nonatopic families. However, greater intimacy of exposure to cats when they were present may have been a factor because cats, significantly more often than dogs, were inside the house and in the child's bedroom. Two subgroups were examined to determine whether those with cat sensitivity who owned cats had more severe symptoms than those with dog sensitivity who owned dogs. Numbers were small and differences not statistically significant, but those in the cat subgroup more frequently had persistent allergic nasal symptoms and abnormally low spirometric measurements than did those in the dog subgroup. Our findings indicate that children are more often allergic to cats than to dogs and suggest that the greater frequency of sensitization to cats may be due to increased intimacy of exposure to cats.

Adolescent↗
PubMed1983

Diagnosis of house dust mite allergy in asthmatic children: what constitutes a positive history?

Standardized questions were put to the parents of 530 children, referred consecutively for evaluation of asthma, to determine which features in the history were associated with house-dust mite allergy. Bronchial challenge tests performed on 19 of the children confirmed that there is a highly significant association between a positive skin prick test and a positive bronchial challenge test to Dermatophagoides farinae mite antigen. One hundred and eighteen (23%) of the children had positive prick tests to the mite. There is a highly significant association between a positive prick test to mite and a history that the subject's respiratory symptoms become worse when there is exposure to domestic activity that stirs up house dust (vacuuming, dusting, sweeping, making the bed, or shaking out blankets) or that the symptoms improve when out of doors. Seasonal variation and other features in the history are of little value in distinguishing mite-sensitive from mite-insensitive asthmatics. Although the 4% whose only positive prick test reaction was to mite had significant worsening of asthma during the colder months compared with the remainder, most mite-positive subjects had multiple allergies and had no characteristic seasonal pattern. The presence of a positive prick test to mite was not associated with aggravation of asthma either at night in bed or in the morning on awakening. A history similar to that of mite-sensitive subjects was elicited in those with a positive prick test to house dust. A positive history of house dust or house-dust mite allergy in asthmatics is one in which respiratory symptoms become worse during domestic activity that stirs up house dust or improve when outdoors.

Adolescent↗
PubMed1983

Dust-free bedrooms in the treatment of asthmatic children with house dust or house dust mite allergy: a controlled trial.

Twenty asthmatic children with prick tests positive for house dust or house dust mites were allocated to two groups that were matched for severity. One group was provided with zippered vinyl covers for pillows, mattresses, and box springs, and instructions for making the bedroom as easy to keep clean as a hospital ward; the other group was not. At the end of a 1-month study period, there was a marked and statistically significant difference in symptoms and signs of asthma between the two groups. Those with a dust-free bedroom had fewer days on which wheezing was observed, medication was given, or an abnormally low peak expiratory flow rate was recorded. Bronchial tolerance to aerosolized histamine significantly improved in the group whose bedrooms had been modified. A dust-free bedroom diminishes bronchial irritability and is a practical and effective method for decreasing asthma in children with house dust or house dust mite allergy.

Asthma↗
PubMed1982

Short stature and delayed skeletal maturation in children with allergic disease.

The frequency of short stature was assessed in 598 children (66% boys, 34% girls) referred consecutively because of asthma or allergic rhinitis. Six percent were of small stature, with heights of less than the third percentile for age. A total of 66 children with small stature were subsequently studied, 36 of whom had asthma. None had received steroids. Children with short stature were predominantly boys (83%, p less than 0.005) and had delayed bone age (less than 2 SD of mean, 34/45), correspondence of bone age with height age (r = 0.93), normal serum thyroxine but increased tri-iodothyronine levels (11/24), and normal insulin-induced growth hormone secretion (12/12). Their heights corresponded only in part to midparental height. The results were the same for those with and without asthma, and the severity of asthma was not related to the degree of growth retardation. The findings suggest that short stature is more common than expected in children with allergic respiratory disease, both asthmatic and nonasthmatic, that their growth potential is good, and that impaired linear growth is not necessarily a result only of asthma but of a more fundamental abnormality possibly associated with the atopic state. They emphasize the importance of considering allergic respiratory disease in the clinical evaluation of children with small stature.

Adolescent↗
PubMed1981

Airway responsiveness to histamine as a test for overall severity of asthma in children.

Seventy-eight children who had a history of asthma were studied while they were symptom-free. There was a highly significant correlation between the dose of aerosolized histamine that produced a decrease in FEV1 of 20% and each of the features in the history that indicated severity of asthma. The correlation was strengthened by the combination of these features into a weighted asthma history score. None of the subjects with mildly increased bronchial reactivity had a history score of severe asthma, and none with markedly increased bronchial reactivity had mild asthma. There was also a highly significant correlation between histamine dose and the results of spirometric tests for airway obstruction. However, the correlation between asthma history score and provocative histamine dose was highly significant even in the 21 subjects who were apparently free of airway obstruction at the time of testing. Furthermore, the correlation between asthma history score and histamine dose was stronger than that between asthma score and any spirometric test, indicating that the histamine test more accurately assessed the overall severity of the asthma. Measurement of bronchial responsiveness to histamine is a useful adjunct to history in determining the severity of asthma in an individual and should be considered as an objective way of grading subjects according to severity of asthma in a clinical study.

Adolescent↗
PubMed1981

Modulation of immunoglobulin M and G synthesis by monocytes and T lymphocytes in the newborn infant.

The role of peripheral blood T lymphocytes and monocytes in modulating Ig synthesis by B lymphocytes stimulated to become Ig-secreting plasma cells by pokeweed mitogen was studied using a sensitive enzyme-linked immunosorbent assay of IgM and IgG in healthy newborn infants and in adult controls. Neonates' B lymphocytes alone synthesized 20 to 30 times less Ig than adults' cells. Increasing proportions of autologous adults' T lymphocytes relative to B lymphocytes initially enhanced and then suppressed Ig synthesis, whereas autologous infants' T lymphocytes had no significant effect. Neonates' T lymphocytes cultured with adults' B lymphocytes enhanced and suppressed Ig synthesis comparably to adults' T lymphocytes, but neonates' B lymphocytes responded poorly to the helper effect of adults' T lymphocytes. Adults' monocytes diminished the helper and increased the suppressor effect of adults' and infants' T lymphocytes on adults' B lymphocytes, whereas neonates' monocytes cultured with neonates' T lymphocytes suppressed synthesis of IgG by neonates' B lymphocytes but had no effect on IgM. The findings suggest that the low serum Ig levels of the newborn period result primarily from immaturity of B lymphocytes rather than from T lymphocyte suppression of Ig synthesis. The normal sequential development of IgM followed by IgG may be a result of gradually increasing responsiveness by neonates' B lymphocytes to the helper effects of newborn T cells. Synthesis of IgG in the newborn infant also appears to be modestly suppressed by T lymphocytes and monocytes, which may contribute to the predominance of serum IgM.

Adult↗
PubMed1981

A comparison of spirometric measurements in allergen bronchial challenge testing.

We compared the usefulness of several spirometric measurements in detecting asthmatic reactions after allergen bronchial challenge in fourteen asthmatic children. All of the children had a history suggesting mite-induced asthma and eleven had a 3 mm or larger diameter weal on prick testing with Dermatophagoides farinae extract. On bronchial challenge testing with dilutions of this extract twelve children had an early asthmatic reaction and nine had a late asthmatic reaction. In decreasing order of sensitivity for detecting the early asthmatic reaction the tests ranked as follows: FEV1, FEF50%, FEF25-75%, PEFR and FVC. For the late asthmatic reaction the order was FEF50%, FEV1, FEF25-75%, PEFR and FVC. No single test identified all the early or all the late reactions but the FEV1, a test useful for indicating large airways obstruction, when combined with the FEF25-75%, a test influenced by small airways obstruction, detected all early and late asthmatic reactions. The FEF50% was a sensitive test but was the only one to become falsely positive. It became falsely positive in four patients. Although the FEV1 was the most useful single test the results suggest that it is, by itself, an inadequate indicator of the asthmatic reaction and that it should be used with the FEF25-75% to ensure the detection of all asthmatic reactions induced by allergen bronchial challenge testing.

Adolescent↗
PubMed1978

Cellular immunity and nutrition in refractory disseminated blastomycosis.

In a previously healthy 13-year-old girl with disseminated blastomycosis, immunodeficiency was considered because of lymphopenia and the slow response of her lung disease to therapy with amphotericin B. Cellular immunity was found to be profoundly impaired, with absent delayed cutaneous hypersensitivity to several common antigens, a decreased count of thymus-dependent lymphocytes in the peripheral blood and a greatly diminished in-vitro proliferative response of lymphocytes to phytohemagglutinin (PHA). Humoral immunity was intact. Two additional types of therapy were assessed: subcutaneous injection of transfer factor was associated with an unsustained increase in lymphocyte counts and a positive cutaneous response to PHA but no clinical change; parenteral alimentation to ensure an adequate energy intake was associated with rapid clinical improvement, the development of delayed hypersensitivity to four additional antigens, and the return of lymphocyte counts and proliferative response to normal. These findings suggest that increased energy intake rather than transfer factor therapy was responsible for the child's recovery, and they emphasize the importance of adequate nutrition in the maintenance of intact cellular immunity.

Adolescent↗